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Prenatal multivitamins help pregnant moms to fill gaps in their diet and meet their own—and their baby’s—special nutritional needs. Now researchers have found a link between taking multivitamins around the time of conception and prevention of early births and births of babies born smaller than normal for their gestational age.

Nearly 36,000 women participating in the Danish National Birth Cohort, a large ongoing study of pregnant women and their children, were included in the study. All of them reported using multivitamins, just folic acid supplements, or no supplements in the 12 weeks around conception: 4 weeks before the last menstrual period until 8 weeks after.

Multivitamins improve the odds

The women were followed until after delivery and were monitored for preterm births (delivery before week 37 of pregnancy) and births of babies that were small for gestational age (weight, length, or head circumference below the tenth percentile for the number of weeks of pregnancy). These are important measures of newborn health because infants born preterm or small for gestational age are at greater risk for a wide variety of health and developmental problems.

When the researchers looked at birth outcomes and vitamin use, they found the following:

Taking multivitamins around the time of conception was associated with a 17% lower risk of small-for-gestational-age births in all women. This effect was strongest in women who took multivitamins in the weeks after conception.

In women who were not overweight prior to pregnancy, taking multivitamins around conception was associated with a 16% lower risk of preterm birth.

Multivitamin use did not affect risk of preterm delivery in women who were overweight prior to pregnancy. (These women are already less likely to deliver preterm.)

Taking folic acid alone had no effect on risk of preterm or small-for-gestational-age births.

Having a healthy pregnancy and birth

“It may be that multivitamin use around the time of conception could be a safe and simple strategy to improve pregnancy outcomes,” the study’s authors said in the American Journal of Clinical Nutrition, while pointing out that more research is needed to show this definitively.

In addition to a multivitamin, there are a few other key supplements that you can consider taking during pregnancy:

Omega-3 fatty acids. We get these from eating fish, but due to pollutants like mercury and PCBs, pregnant women should eat fish judiciously (perhaps no more than 2 helpings a week). Supplementing with omega-3 fats during pregnancy has been shown to help ensure full-term births and healthy-sized newborns.

Vitamin D. Most of us don’t get enough sun all year to maintain healthy levels of vitamin D, and some research suggests that pregnant women with low vitamin D levels are more likely to deliver preterm.

Iron, folic acid, and zinc. Low levels of these nutrients during pregnancy are associated with poor birth outcomes. If you don’t take a prenatal multivitamin, remember to stay on top of these nutrients.

(Am J Clin Nutr 2011;94:906–12)

Maureen Williams, ND, completed her doctorate in naturopathic medicine at Bastyr University in Seattle and has been in private practice since 1995. With an abiding commitment to access to care, she has worked in free clinics in the US and Canada, and in rural clinics in Guatemala and Honduras where she has studied traditional herbal medicine. She currently lives and practices in Victoria, BC, and lectures and writes extensively for both professional and community audiences on topics including family nutrition, menopause, anxiety and depression, heart disease, cancer, and easing stress. Dr. Williams is a regular contributor to Healthnotes Newswire.